The temperature in a well bore generally increases with increase in depth of the well bore. As an example, some well bores along the Texas Gulf Coast will have temperatures in excess of 300.degree. F. at 15,000' depth.
Some electrical components will fail at temperatures above 250.degree. F.; other components will survive until temperatures of 300.degree. F. or greater is encountered. Almost all electrical components become subject to failure at temperatures in excess of 400.degree. F.
There have been various approaches to protecting the electronic components from the excessive heat in well bores. One approach has been to insulate the electronics from the surrounding well bore and also to provide a "heat sink" in with the electronics to absorb such heat as passes through the insulation.
As another approach, the "vacuum bottle" or Dewar type insulated enclosure has been commonly used. The heat sink utilized has been either a eutectic material or some metal, such as brass. One such eutectic substance has a trade name of "Cerrobend" which is a composition including cadmium, bismuth, lead and tin in proportions such that the melting temperature is about 158.degree. F.
Another kind of apparatus which is used to remove heat from a particular environment is commonly called a "heat pipe". The heat pipe is an elongated tube having a wick running through its length with one end of the tube being in the hot environment and the other end being in a cooler or cold environment. The tube is charged with a selected amount of liquid having a particular boiling point such that the liquid will boil in the hot environment and give off vapors which will travel through the tube into the colder environment. In the colder environment the vapors condense back into the liquid which is soaked up by the wick and transferred through the wick by capillary action back to the hotter environment where the evaporating cycle is repeated. Such heat pipes can be very efficient so long there is an appreciable difference in the temperatures of the hot environment and the cool environment.
Prior art cited in the parent of this application was deKanter U.S. Pat. No. 4,407,136 Krempl U.S. Pat. No. 4,169,387, Noran U.S. Pat. No. 3,714,981, and Camarda U.S. Pat. No. 4,485,670. No more pertinent prior art is known.